Stabilized mineral oils and method of preparation



STABILIZED MINERAL OILS AND METHOD OF PREPARATION Kurt Binovic, Boulogne, and Robert Dupas, Notre Dame de Gravenchon, France, assignors to Esso Standard Societe Anonyme Francaise, Paris, France, at body corporate No Drawing. Application February 19, 1952, Serial No. 272,516

Claimspriority, applicationFranceE February 21', 1951 9 Claims. (61. 196 -151) The present invention relates to stabilized mineral oils and a method for improving the stability to oxidation of mineral oils, and more especially those mineral oils which have been refined with sulphuric acid or oleum.

It is known that the refining of mineral oils, particularly insulating oils and certain turbine oils, requires a more or less severe treatment. with sulphuricacid to give them certain desirable qualities among which is. good stability during service.

Experience has proved, however, that there is an optimum treatment beyond which the stability diminishes, i. e. beyond which the acid index increases too rapidly in use. It results from this that if a severe sulphuric acid treatment is necessitated by the color or insoluble deposits, the oil obtained is insufiiciently stable; particularly as regards. the development of, acidic products and consequent increase in the acid index during service.

To obviate this, it has often been advocated to add to oils of low stability to oxidation, .difierent fractions of petroleum in proportions varying between 10 and 50%. In this way there has been advocated, with the object of increasing the stability to oxidation of mineral oils, the use of unfinished cylinder oils or Bright stock or different solvent extracts, obtained from medium fractions of petroleum, after-treated with acid or activated. earth.

The addition of large proportions of other petroleum fractions to finished oils frequently may be very incon-' venient. In particular, in the case of special highly refined oils for which the improvement obtained is made to the detriment of other qualities the properties of the oil, such as viscosity, flash and freezing point, may even be completely changed. Moreover, the expenses of adding large proportions of other petroleum. fractions may prevent the economic use of this method of stabilizing mineral oils. On the other hand, the addition of relatively very small quantities of. other fractions is not objectionable though commonly considered ineffective.

It has now been discovered that the stability of mineral oils to oxidationHcan-he improved by :the addition of up to 1% by volume of a heavy oil fraction obtained by deasphalting a heavy residual oil from the distillation of crude petroleum. The invention is applicable to mineral oils generally but particularly to those fractionsof moderate viscosity, i. e., of the insulating oil-lubricating oil range.

The heavy residual oil may be obtained as the residue on distilling crude petroleum under vacuum. The de- '7 asphalting of the residualoilmay becarried out by known means, preferably by the use of propane.

The deasphaltised heavy'oil residuum is preferably used for purposes of the present invention: in amounts of between 0.1 and 1% by volume of the mineral oil to be stabilized. Proportions as low as 001% may be usedfor some purposes.

.It has also been discovered that even more pronounced stabilizing effects are produced by treating the ,deasphalt- L 2,725,345 Patented Nov. 29, 1955 ised heavy oil residual. oils with a selective solvent such as phenol, furfural or preferably tetrahydrofurfuryl alcohol.

The antioxidant effect of the deasphaltised heavy residual oil and of the fractions obtained from such deasphaltised :heayy residual oils byditt'erent treatments have been tested on a mineral insulatingv oil, obtained by the sulphuric acid refining of a light distillate from a Coastal crude.

The characteristics of the insulating oil which was treated were as follows:

Density at 15 C. ,t.,.,. 1- 0.88} Englerviscosity at20 C., 4. 69. Flash (Cleveland) i ...t 164/182? ,0. Tag-Robinson colon-.. 24 Thomsonv tar. ,,.,,,k, ,t 0.016; Freezing point... 48 C. Acid index 0.0.1

The oxidation tests were carried out according to the Staeger Life Test,? slightly modified.

The .oil or mixture of- .oils (200 cc.) was oxidized in an oven with a revolving floor (4 6 R. P. M.) at ":05" C;, a current of, purified air at 4754 litres per; hour passing through the: oven, and in presence of plates of polished electrolytic copper of 40x70x0.1- mm. replaced every 7-2 hours.

Samples of .20 gm, of oil-were taken after 72, 144. and 192 hours of. oxidation and. the acid index was measured. The color (.1 .ag-Robinson) was. measured after, l92hours. The acid index and color-were measuredbefore the oxidation.

Measurements of stability were also carried out according to the method eithe Brown Boveri Company, as shown below.

There will be given hereafterexamples, in no: way limiting, which will better illustrate the features of the invejntion.

Example- I A petroleum from Arabia (Aramco) v was distilled under vacuum until only 14% of-residuewasleft. This latterwas taken up in 800% by volume of propane and allowed to separate at- 45? After separation of the asphalt, the upper layer was collectedand the propane separated by distillation: There was thus 'obta'ined'8% of a very viscous-oil. i i

0.1% of this deasphalted residue was added to the insulating oil described above.

Thi mixture and h nsulatingroil Without addition were submitted ,totoxidation according to. the modifie Staeger Life Tests. o

The resultsobtainedwere as. follows:

The insulating oil and its mixture with 0.1% 015 deasphaltised residual oil stock were also oxidized according to the method of the Brown Boveri-ompany-.

The results were as follows:

Decrease In 1 Acid Index mg. KOH Insoluble per gm. 011 Deposit gggg Composition Before After After After After After After Oxida- 72 168 72 168 72 168 tion Hrs. Hrs. Hrs. Hrs. Hrs. Hrs.

Insulating Oil 0.056 0.28 0.002 0.042 30 50 Insulating 0ll+0.1% Deasphaltlsed Heavy Residual Oil 0 0. 042 0.155 None 0.03 27 32 Example 11 increase their stability as indicated by substantial reduc- The deasphalted heavy residual oil stock, obtained as indicated in Example I was treated with 400% of phenol in countercurrent at 70 C. The upper phenol-free layer (raffinate) was then added in an amount of 0.1% by volume to the insulating oil, and this mixture and the pure insulating oil were oxidized according to the modified Staeger Life Test.

The results obtained were as follows:

The same trials carried out according to the Brown tions in the amounts of organic acids and insoluble deposits formed during service. Moreover, the color is seen to be improved slightly after oxidation.

Solvent treatment of the deasphaltised heavy residual oils with tetrahydrofurfuryl alcohol is seen to improve the stability of mineral oils to which they are added, even more. a

What is claimed is:

1. An oil composition of high oxidation resistance comprising a mineral base oil fraction of insulating-lubricating oil viscosity grade containing 0.01 up to 1% by volume of a propane deasphalted residual oil from the distillation of crude petroleum.

2. Composition as claimed in claim 1 wherein there is present from 0.1 to 1% by volume of the deasphalted residual oil.

3. Compositions as claimed in claim 2 wherein the deasphalted residual oil is first subjected to a selective solvent extraction treatment.

4. Composition as claimed in claim 3 wherein the sol- Boveri Company test had the following results: vent used is tetrahydrofurfurylalcohol.

Decrease In Acid Index mg. KOH Insoluble per gm. Oil 7 Deposit ggg Composition Before After After After After After After Oxide- 72 168 72 168 72 168 tion Hr. Hr. Hr. Hr. Hr. Hr.

Insulating Oll 0 0. 056 0. 28 0. 002 O. 042 30 50 Insulating 0il+0.1% Raflinate 0 0.042 0.15 None 0.015 10 40 Example III 5. Compositions as claimed in claim 3 wherein the sol- The deasphaltised heavy residual oil stock, obtained as described in Example I, was treated with 100% of tetrahydrofurfuryl alcohol at room temperature. After some hours of decantation, the two layers were separated.

The lower layer (extract) was freed from tetrahydrofurfuryl alcohol by distillation. The fraction so obtained was added in an amount of 0.4% by volume to the insulating oil. This oil and the mixture were submitted to oxidation according to the modified Staeger Life Test.

The results were as follows:

It may be seen from these results that the addition of deasphaltised heavy residual oil stocks to mineral oils vent used is phenol.

6. A method of stabilizing mineral oils of insulatinglubricating oil viscosity range against oxidative deterioration comprising adding between 0.01 and 1% of a propane deasphalted residual oil from the distillation of 'crude petroleum.

7. A method as claimed-in claim 6 wherein the deasphalted residual oil is first subjected to a selective solvent extraction treatment.

8. A method as claimed in claim 6 wherein the deasphalted residual oil is first. subjected to a selective solvent extraction treatment with tetrahydrofurfuryl alcohol.

9. A method as claimed in claim 6 wherein the deasphalted residual oil is first subjected to a selective solvent extraction treatment with phenol.

UNITED STATES PATENTS References Cited in the file of this patent 1,833,374 Hill Oct. 18, 1932 2,117,602 Bulkley May 17,.1938 2,139,668 Breth et al Dec. 13, 1938 2,165,432 Whiteley July 11, 1939 2,195,659 Shoemaker Apr. 2, 1940 2,200,534 Bray May 14, 1940 2,295,035 Gilbert et'al. Sept.'2, '1942 

1. AN OIL COMPOSITION OF HIGH OXIDATION RESISTANCE COMPRISING A MINERAL BASE OIL FRACTION OF INSULATING-LUBRICATING OIL VISCOSITY GRADE CONTAINING 0.01 UP TO 1% BY VOLUME OF A PROPANE DEASPHALTED RESIDUAL OIL FROM THE DISTILLATION OF CRUDE PETROLEUM. 